JPH0429873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a fuel injection nozzle for an internal combustion engine, comprising a valve needle loaded by a closing spring, the valve needle being loaded by fuel pressure in the opening direction and The damper is coupled to a damping device, the damping device being configured to damp the movement of the valve needle during the opening stroke in accordance with at least one operating parameter of the internal combustion engine, while substantially not damping the movement during the closing stroke. , the damping device has a cylinder and a piston delimiting a buffer chamber filled with fuel, and the relative relationship between the cylinder and the piston caused by the valve needle movement during the opening stroke when the volume of the buffer chamber is damped is variable by the movement, in which case the fuel flows into or out of the damping chamber only via the throttle cross section, and the damping device is furthermore provided with a return spring, which The return spring acts on one of the components delimiting the buffer chamber after the closing stroke has begun and returns this component to the starting position against the flow resistance of the throttle cross section.

European Published Patent No. 0084662 (Form 54(3)EP
In fuel injection nozzles for internal combustion engines according to U¨ (unpublished document), the opening cross section of the injection nozzle is controlled in order to adapt it to the different demands of the internal combustion engine at different speeds and load conditions. The valve needle is connected to a shock absorber. In order to prevent extremely long injection periods from occurring in the high speed ranges or load ranges of the internal combustion engine, a damping device with a damping chamber loaded via a throttle, formed by a piston and a cylinder, is used. The design is such that the impact effect is canceled already before the valve needle opening stroke ends.

Although this significantly shortens the overall duration of the injection process, the point at which the damping effect is overridden must be determined in relation to the needle stroke and thus the difference between idling and full-load operation of the internal combustion engine. The problem arises that a certain degree of compromise must be accepted between the parties.

The object of the invention is to make it possible to harmonize the parameters of the injection nozzle that influence the damping effect in a desired manner in order to automatically adapt the damping effect to the operating demands in different operating states of the internal combustion engine;
In this case, the damping effect can be changed by shifting the damping start time with respect to the injection start time.

According to the invention, the component which is loaded by the return spring on the upper side of the return spring and the throttle cross section (a predetermined rotational speed and/or injection quantity needle stroke) then performs valve needle opening. The solution is that they are adapted to each other in such a way that at the beginning of the journey they first travel part of the remaining journey to the starting position.

The embodiment of the invention provides the advantage that in all operating states of the internal combustion engine, the opening movement of the valve needle is damped in a manner that satisfies the demands and that the injection period is automatically adjusted.

Furthermore, the embodiment of the invention advantageously provides the advantage that the damping effect can be varied by shifting the damping start time with respect to the injection start time. As a result, although a long injection period is maintained at low rotational speeds or injection quantities, at high rotational speeds and large fuel quantities the entire duration of the injection process is maintained from the beginning of the valve needle. It can be further shortened compared to the case where it is buffered. According to the invention, therefore, even during full-load operation of the internal combustion engine, the duration of the injection process can be shortened in such a way that when adapting the injection device to the operating conditions, the injection duration can be varied over a wider range than before. Furthermore, the injection period can be influenced independently of each other at low and high speeds. Furthermore, the damping device itself can be constructed in any known advantageous manner.

As claimed in claim 2, the piston of the damping device is constituted by the inlet end section of the valve needle and the cap is placed over this end section as a cylinder. A simple and lock-free construction is obtained by using the .

The stroke number and/or stroke length of the valve needle or the injection quantity injected per injection stroke can be detected in a simple manner by means of a time-distance element connected to the valve needle and can be used to control the damping device. . The time-distance member is moved from a first end position to a second end position during the closing stroke of the valve needle and is then returned to the first end position at a reduced speed by a return spring. Furthermore, the time-distance element reactivates the damping device during the subsequent opening stroke of the valve needle, once the valve needle has reached its first end position again in a slowed return.

This design is based on the recognition that as the rotational speed increases, the time between two injection processes shortens and that the stroke of the valve needle increases in the case of large injection quantities. Taking into account that the return of the time-distance element in each case begins at the beginning of the closing stroke of the valve needle, the point in time for activating the damping device for the subsequent opening stroke of the valve needle is at the beginning of the opening stroke. On the other hand, the larger the dedicated valve stroke and the shorter the time between successive strokes, ie the higher the rotational speed of the internal combustion engine, the more the delay is delayed. The valve needle therefore carries out an undamped partial stroke at the beginning of the opening stroke, the length of which is automatically adapted to the respective operating parameters of the internal combustion engine.

Furthermore, it can be provided that the damping effect remains effective over the entire opening stroke of the valve needle only in the lower speed and load ranges or at the idle critical rotation point. In many cases, it is advantageous to provide a minimum retarding effect of the damping device, ie a minimum free stroke of the valve needle, which minimum free stroke is provided at every operating point of the internal combustion engine.

Furthermore, a simple and space-saving construction is obtained by the fact that the cylinder and the piston of the damping device simultaneously form a time-distance element that is activated during the closing stroke of the valve needle. In this case, the cylinder and piston perform the function of a damping device during the damped partial stroke of the valve needle, whereas during the rest state and the undamped movement of the valve needle,
It performs the function of a time-distance component that produces a buffering effect with a delay relative to the operating point of the internal combustion engine.

The invention will now be explained with reference to the drawings: The injection nozzle shown in FIG.
The nozzle body 10 is fastened to a nozzle holder 14 by a cap nut 12. A slube 16 is arranged between the nozzle body 10 and the nozzle holder 14. This sleeve 16 has inwardly directed shoulders 18.

A shoulder 18 divides the interior chamber 20 of the injection nozzle from a larger diameter chamber 22 . A valve seat 24 is formed in the nozzle body 10, and a valve needle 26 is movably supported. This valve needle 26
The sealing cone 27 of the valve seat 2 is closed by a closing spring 28.
It is pressed to 4. The closing spring 28 rests on the nozzle body 10 and acts via a flange part 30 on a support disk 32 . This support disk 32 itself rests on a shoulder 34 of the valve needle 26.

A supply hole 36 is formed in the nozzle holder 14,
The supply hole 36 opens into the chamber 20 which is connected to the chamber 22 through an opening 38 surrounded by the shoulder 18.
is connected to. The chamber 22 communicates via a bore 40 provided in the nozzle body 10 with an annular chamber 42 which is connected to the central bore wall of the nozzle body 10 and to the outer circumferential surface of the reduced diameter section 44 of the valve needle 26. and reaches in front of the valve seat 24. Between the flange portion 30 and the nozzle body 10 there is a valve needle 26 in the illustrated closed position.
An interval hg corresponding to the entire stroke is provided.
The valve needle 26 is moved by the fuel pressure to the flange portion 3.
0 is moved against the closing spring 28 in the opening direction until it comes into contact with the nozzle body 10. When the valve is closed, the closing spring 28 brings the valve needle 26 inwardly into the closed position shown.

A piston-shaped extension 46 is connected to the shoulder 34 of the valve needle 26, which extends into the opening 3.
8 and rushed into chamber 20. The diameter of the piston-shaped extension 46 corresponds to the guide diameter of the valve needle 26. A cap 48 is placed over the extension 46 and has a bottom 50, a peripheral wall 52, and a flange edge 54. A return spring 56 acts on the cap 48, surrounding the peripheral wall 52 and pressing the flange edge 54 against the shoulder 18 of the sleeve 16.

A lateral slit 58 is provided in the flange edge 54 of the cap 48 and the peripheral wall 52 connected thereto. Fuel always flows through this horizontal slit 58.
Chamber 20 to Chamber 2 also when the valve needle is closed.
2. A buffer chamber 60 is formed within the cap 48 between the end surface of the additional portion 46 and the bottom portion 50. This buffer chamber 60 has a throttle hole 62 in the bottom portion 50.
It is constricted and connected to the fuel flow path through.
In the illustrated closed position, the extension 46 covers the transverse slot 58 by a distance hi in the axial direction. This distance hi is selected to be greater than the total stroke hg of the valve needle 26. However, it is also possible for the distance hi to be smaller than the total stroke hg by a minimum value, such that at the end of the opening stroke of the valve needle 26 there is still a slightly undamped partial stroke.

The aperture hole 62 is partially or completely connected to the cap 4.
This could also be replaced by a suitable radial play between 8 and extension 46. The cap 48 of the piston-shaped extension 46 of the valve needle 26 forms at the same time a member for damping valve needle movements and a time-distance member. This time-distance element relates the damping onset timing to the rotational speed and the magnitude of the valve needle stroke. The damping action and the action of the time-distance member are achieved by suitably matching the return spring 56 and the throttle hole 62 and by regulating the inflow of fuel into and outflow of the damping chamber 60. is determined by the parameters of

The illustrated injection nozzle works as follows.

Due to the rising fuel pressure at the beginning of the first injection process, a pressure difference immediately arises between buffer chamber 60 and chamber 20. This is because cap 48 does not follow the movement of valve needle 26. In this case, the pressure rise in the buffer chamber 60 is slower than the pressure rise in the chamber 20, so that the movement of the valve needle 26 is such that during this first injection stroke the valve needle 26 may travels the distance hi, and the additional part 4
6 is decelerated or damped from the beginning until it reaches the range of the lateral slit 58. When the end face of the extension 46 reaches the range of the lateral slit 58, the valve needle is Travel unbuffered with minimal residual travel. The illustrated position of cap 48 will hereinafter be referred to as cap 4.
This will be referred to as the first end position of 8.

During the opening stroke of the valve needle 26, fuel is sucked or forced into the buffer chamber 60 through the throttle hole 62. In the next closing stroke, the cap 48 is moved upwardly through the fuel cushion in the buffer chamber 60 to a position hereinafter referred to as the second end position. In this case, the return spring 56 offers relatively little resistance against the much stronger closing spring 28, so that the closing stroke takes place almost undamped. From the beginning of the closing stroke, the return spring 56 pushes the cap 48 back towards the end face of the extension 46. In this case, the amount of fuel that had flowed into the buffer chamber 60 is pushed out of the buffer chamber 60 again. This can only be done at a certain degree of deceleration because the throttle hole 62 is narrow. Cap 48 1st
The distance between the end position and the second end position is such that the distance between the end position of
8 corresponds approximately to the valve needle stroke which has been reduced by a small residual stroke displaced under the force of the permanently active return spring 56.

The operation of the time-distance member formed by cap 48, buffer chamber 60 and return spring 56 is illustrated in FIGS. 2-4. In each case, the course of the valve needle stroke is shown as a solid line h, and the course of the deflection of the cap 48 is plotted as a dashed line a over time t. In both figures, the closed position of the valve needle 26 and the first end position of the cap 48 shown in FIG. 1 lie on the time axis t.

Time t ₁ (FIG. 2) is the point at which the closing stroke of valve needle 26 begins. In this case, cap 48
is moved from a first end position E ₁ to a second end position E ₂ . Cap 48, as already mentioned, travels a distance ag which is somewhat less than the total stroke hg of valve needle 26. The closing process ends at time _t2 . From there, cap 48 begins to return at a predetermined speed under the force of return spring 56, indicated by angle α in the drawing.

At time t ₃ a new opening stroke of valve needle 26 begins. As shown in Figure 2, at time t ₃
If the cap 48 has not yet reached its first end position, the cap 48 is returned to this end position at approximately the same speed as the valve needle 26. cap 48
is in its first terminal position at time _t4 . From there, the cap 48 is held by the shoulder 18 so that it does not follow the movement of the valve needle 26 in the opening direction.
The aforementioned damping member becomes effective again. This is represented in the drawing by the fact that the stroke course line has an inflection point K at time _t4 . From time t ₄ onwards, the valve needle 26 is brought into its end-of-stroke position at a damped, ie reduced speed. The described process is then repeated anew.

3 and 4 show that the damping device according to the invention can be automatically adapted to different operating conditions of the internal combustion engine.

In FIG. 3, the internal combustion engine is operated at a low speed and with a low load, so that the cap 48 already reaches its first end position before the next opening stroke begins. In this case, the damping is effective over the entire opening stroke of the valve needle 26. In Figure 4, the internal combustion engine is operated at high speed and with a large load.
An operating situation is shown in which the valve needle stroke is also significantly adjusted. In this case, the next opening stroke is started before the cap 48 returns to its first end position. The inflection point K of the stroke course h of the valve needle 26 is shifted closer to the end-of-stroke position than in the operating state of FIG. 2, so that even a small part of the opening movement of the valve needle 26 is damped. It's summery.
As can be seen from FIG. 4, the injection process continues with a smaller time interval to the next injection process, and the greater the valve needle stroke, the closer the inflection point K is to the end of the opening stroke of the valve needle.

The cap 48 is centered with respect to the valve needle 26 and has a sufficiently large radial play with respect to the nozzle holder 14 so that the valve needle 26 works without being locked. Return spring 5
6 extends beyond the cap 48, so that in this embodiment the means for partially damping the opening stroke of the valve needle 26 require little space in the axial direction of the injection nozzle.

[Brief explanation of drawings]

The drawings show a plurality of embodiments of the present invention, in which FIG. 1 is a longitudinal sectional view of an injection nozzle of a diesel internal combustion engine, and FIGS. 2, 3, and 4 are cross-sectional views of the injection nozzle of FIG. 1. It is a figure which shows the function of a buffer member. 10... Nozzle body, 12... Cap nut, 14
... Nozzle holder, 16 ... Sleeve, 18 ...
Shoulder, 20...chamber, 22...chamber, 24...valve seat, 2
6...Valve needle, 27...Seal cone, 28
...Closing spring, 30...Flange part, 32...
Support disc, 34...shoulder, 36...supply hole, 38...
...opening, 40...hole, 46...additional part, 48...
Cap, 50...bottom, 52...peripheral wall, 54
... Flange edge, 56 ... Return spring, 58 ... Horizontal slit, 60 ... Buffer chamber, 62 ... Throttle hole.

Claims (1)

Claims: 1. A fuel injection nozzle for an internal combustion engine, comprising a valve needle 26 loaded by a closing spring 28, which valve needle is loaded by fuel pressure in the opening direction and equipped with a damping device. The damping device is configured to damp the movement of the valve needle in dependence on at least one operating parameter of the internal combustion engine during the opening stroke, while substantially not damping it during the closing stroke; The device has a cylinder 48 and a piston 46 delimiting a buffer chamber 60 filled with fuel, produced by the valve needle movement during the opening stroke when the volume of the buffer chamber is buffered. is variable by the relative movement between the damper and the damper, in such a way that the fuel flows into or out of the buffer chamber 60 only via the throttle cross section 62; A return spring 56 is provided, which returns after the closing stroke has begun.
In a version that acts on one of the components 48, 46 delimiting the buffer chamber and returns this component 48, 46 to the starting position against the flow resistance of the throttle cross section 62, the return spring 56 and the throttle Cross section 62
and above a predetermined rotational speed and/or injection quantity, the component 4 is loaded by the return spring 56.
8, 46 are adapted to each other in such a way that they first travel part of the remaining stroke to the starting position at the beginning of the subsequent valve needle opening stroke,
Fuel injection nozzle for internal combustion engines. 2 with a valve needle that is open in the direction of fuel flow, in which the piston 46 of the shock absorber is constituted by the inlet end section of the valve needle 26 itself and is connected to this end section as a cylinder; 2. A fuel injection nozzle according to claim 1, in which a fitted cap 48 is used, a return spring 56 acting on the cap, which co-operates with a stop 18 fixed on the casing. .